SOCIAL ORGANIZATION AND BEHAVIOR
Photo: Erik Patel
Long-term research on and information about social organization and behavioral
patterns in the diademed group of sifakas is limited to studies conducted on
Milne-Edwards' sifakas (P. edwardsi) at Ranomafana National Park.
Milne-Edwards' sifakas have average group size of 4.8 but can have between three
and nine individuals (Wright 1995; 1998). The social structure of these groups
varies based on size and can be polygynandrous, polyandrous, polygynous, or
monogamous. Because group size is so small, variations in composition, such as
an increase in the number of adult females or adult males, necessitate a shift
in the type of social organization or mating system (Pochron & Wright 2003;
Pochron et al. 2004). This flexibility may be related to environmental factors
such as increased feeding competition for seasonal resources and the presence of
predators. One explanation for group living in primates is increased vigilance
and detection of predators; it is safer for animals to travel in groups than as
single individuals. Where there are predators and highly seasonal resources,
though, group size may be limited because of increased feeding competition
between group members. Sifakas may balance the need for predator protection
with minimal feeding competition by keeping group size small and shifting the
organization throughout the year to enhance mating opportunities (Pochron &
Wright 2003; Pochron et al. 2004).
Brief field studies and rapid censuses provide some information about the social
structure and group composition of silky sifaka (P. candidus) groups.
At Marojejy National Park and Anjanaharibe-Sud Special Reserve, silky sifakas live in
multi-male/multi-female groups and in male-female pairs of 2 to 9 individuals.
Average group size is 4 (Schmid & Smolker 1998; Sterling & McFadden 2000; Patel 2006a).
Adult male immigration and emigration have been observed one time each since 2001 within the
one long-term study group at Marojejy. No adult females have yet been seen to change groups
(ER Patel, pers. comm.). Similarly, the little-studied Perrier's sifaka
(P. perrieri) lives in small groups ranging in size from one to six
individuals and includes adult males and females as well as their offspring
(Mayor & Lehman 1999). Propithecus tattersalli lives in small
groups ranging in size from three to six individuals, but average group size is
five individuals (Vargas et al. 2002). While these species have not been
studied as extensively as other members of the genus Propithecus,
estimates of group size are similar for better studied species such as P.
edwardsi and P. diadema (Meyers & Ratsirarson 1989). Diademed
sifakas (P. diadema) live in female dominated, multi-male/multi-female
groups of up to eight individuals of all ages (Powzyk 1997; Powzyk 2001). About
half of P. edwardsi individuals of both sexes migrate from their natal
group with females leaving before maturity and males both before and after
maturity (Wright 1995; Pochron et al. 2004). Given the similarities in
ecological patterns and group size among sifakas of the diadema group, future
research may reveal similar patterns of social behavior such as group transfer
and dominance patterns.
Daily, the silky sifaka (P. candidus) spends 44.4% of its time resting,
21.9% foraging, 16.8% engaged in social behavior, and spends the rest of the day
sleeping, moving or engaging in other activities (Patel 2006a). P.
diadema spends its time somewhat differently, with 37.8% of its time spent
feeding, 49.4% resting, 2.4% in social behavior, 5.1% moving, and the rest in
other activities (Powzyk 1997).
Photo: Tomas Junek
Most reproductive data for the eastern sifakas are limited to the Milne-Edwards'
sifaka (P. edwardsi) and the golden-crowned sifaka (P.
tattersalli). Sifakas have numerous types of mating system, often at once
and in the same population. P. edwardsi populations can have
polygynous, polygynandrous, polyandrous, and monogamous mating systems at once
during mating season in surprisingly even proportions relative to one another
(Pochron & Wright 2003). As in other Malagasy lemurs, sifakas reproduce
seasonally. Milne-Edwards' and golden-crowned sifakas (P. tattersalli)
mate during the austral summer, in December and January. As would be expected
following seasonal mating, they also show a strong seasonality of births,
usually giving birth during the winter between May and July, with the majority
of births in June (Meyers & Wright 1993; Hemingway 1999; Pochron et al.
2004). P. tattersalli normally mates almost two months earlier than
P. edwardsi during the summer (Meyers & Wright 1993). Copulations
only occur over a 24-hour period when the female is in estrous and fertile.
However, females within a group are fertile on different days (Wright 1995;
Pochron & Wright 2003). Fertility is signaled by an approximately 10-hour
long, externally visible pink genital swelling in females (Pochron & Wright
2003). As the breeding season nears, males also exhibit a testicular volume
increase over any other time of the year (Pochron et al. 2002).
Copulation is short in duration, often between only 30 and 90 seconds and
consists of a single mount (Wright 1995; Pochron & Wright 2002).
Gestation for P. edwardsi averages 179 days (6 months) and gestation
for P. tattersalli is just under six months (Meyers & Wright 1993;
Wright 1995). Age at first birth for P. edwardsi females is around 4
years of age with an increase in fertility at 6 (Meyers & Wright 1993;
Wright 1995; Pochron et al. 2004). Males reach reproductive maturity at 5 years
old (Wright 1995). Interbirth interval for P. edwardsi averages 1.56
years, but due to strict reproductive seasonality, the interval is one year
around half of the time and two years the rest of the time resulting in the
intermediate average (Pochron et al. 2004). Similarly, the interbirth interval
of P. candidus averages 1.67 years (Patel 2006a). The true value of the
inter-birth interval is affected by whether or not the infant survives its first
year (Pochron et al. 2004). In the same vein, infanticide is recorded in P.
edwardsi, possibly as a male strategy to shorten the inter-birth interval
from the two years typical of mothers with surviving infants to one year (Wright
1995; Erhart & Overdorff 1998).
Photo: David Haring
Information about infant development and parental care in the eastern sifakas is
scarce and comes almost exclusively from the Milne-Edwards' sifaka (P.
edwardsi) in the wild. At birth, the species averages 156 g (5.5 oz)
(Glander et al. 1992). Births are synchronous within the group, with 6 of 8
births in one study occurring during a one week window (Pochron & Wright
2003). The infant spends more time on its mother than on other group members
and the mother is the main care provider (Grieser 1992). Although mothers are the
primary caregivers in other sifakas as well, Propithecus non-mothers are known to
engage in substantial infant care on occasion that can include allonursing and carrying.
Amongst sifakas, allonursing has only been observed in P. edwardsi and P. candidus. Less
extreme forms of allocare such as grooming and playing are often seen in both eastern
and western sifakas (Jolly 1966; Grieser 1992; Patel et al. 2003a; reviewed in Patel 2007b).
From birth in P. edwardsi, the infant is carried ventrally, only moving
to a dorsal riding position starting in the third week of life and is
increasingly seen in that position thereafter. Also around this time, the
infant starts to feed and is seen alone and not in physical contact with any
other individuals for the first time. Allogrooming and self-grooming commence
in the fourth week of life. Play starts by week 6 of life but rarely occurs
between the infant and the mother and most often occurs between the infant and a
juvenile. Either way, play with other group sifakas is uncommon (Grieser 1992).
By one year old, juveniles weigh 2500 g (88.2 oz) (Glander et al. 1992).
Infant mortality is high in P. edwardsi, with over half of female
infants dying in their first year of life and only a quarter making it to
reproductive age at four years old (Pochron et al. 2004). At night, mothers
will still sleep with their offspring until the young are two years old (Wright
1995). P. tattersalli mothers will wean their infants 5 months after
birth and P. edwardsi will wean their offspring 6 months after birth
both of which correspond to just slightly before the subsequent breeding season
(Meyers & Wright 1993).
Adult eastern sifakas have a moderately sized vocal repertoire of about 7 call types
(Patel et al. 2005b). Infants have several specialized vocalizations as well. Despite the
relatively small size of their vocal repertoire, some eastern sifakas are highly vocal with high
call rates averaging 7 calls per hour per individual in silky sifakas (ER Patel pers. comm.).
The most frequently emitted vocalizations are low amplitude, low frequency, tonal "hum" and
"mum" vocalizations. These contact calls are used in a variety of circumstances including group
movement, affiliation, foraging, and while resting. The loudest vocalizations produced are
their alarm calls which are often emitted in a contagious or antiphonal fashion by all group
members. Broad-band noisy "aerial disturbance roars" are emitted with open mouths to overhead
raptors and other aerial disturbances such as falling trees and small birds. Sometimes they
stare skyward and drop vertically in the trees while producing these loud aerial roars
(Wright 1998; Patel et al. 2003b). Eastern sifakas also emit a general disturbance alarm call,
the sneeze-like "Zzuss!" vocalization, that is produced with closed mouths in response to lost
calls or "howls" by other group members, terrestrial disturbances, terrestrial predators, and
other high arousal contexts (Wright 1998; Patel et al. 2003b). Acoustic analyses have revealed
sex and individual differences in the acoustic structure of "Zzuss" vocalizations
(Patel et al. 2005c; 2006). In all sifakas, greater context specificity is apparent for aerial
disturbance alarm calls than terrestrial disturbance alarm calls (Fichtel & Kappeler 2002; Patel et al. 2003b);
a pattern also seen in anthropoid alarm call systems such as vervet monkeys (Chlorocebus sp.)
and capuchin monkeys (Cebus sp.) (Seyfarth et al. 1980; Digweed et al. 2005).
LISTEN TO VOCALIZATIONS
- Propithecus candidus: Chatter-squeal during agonism (Erik Patel; Cornell University)
- Propithecus candidus: Howls (Erik Patel; Cornell University)
- Propithecus candidus: Multiple animal aerial roars (Erik Patel; Cornell University)
- Propithecus candidus: Single animal roars (Erik Patel; Cornell University)
- Propithecus candidus: Zzuss call (Erik Patel; Cornell University)
- Propithecus diadema: Chatter, Squeal and Purr (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: Howl (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: Hum (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: MMM (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: Purr (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: Roar (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus diadema: Zzuss (Erik Patel, John Anderson, Mitchell T. Irwin; Cornell and Stony Brook University)
- Propithecus edwardsi: Aerial roars (Erik Patel; Cornell University)
- Propithecus edwardsi: Mmm call (Erik Patel; Cornell University)
As in other prosimians, olfactory communication is well developed in sifakas. Eastern sifakas possess
several specialized scent-marking glands that include a sebaceous chest gland only found in males and
mixed apocrine-sebaceous ano-genital glands in both sexes (Schilling 1979). Sifakas do not allomark,
as in Eulemur, by directly scent-marking conspecifics. Females scent-mark trees by rubbing their
anogenital glands against trees in a rhythmic vertical motion. Males scent-mark trees in several
ways, by rubbing them with their chest gland, ano-genital glands, or a combination of the two
(Pochron et al. 2005b). Males routinely gouge trees with their toothcombs just prior to chest marking
which leaves long lasting visible marks. Eastern sifakas do not eat bark or gum, so such non-nutritive
male tree gouging is likely communicative in function (ER Patel pers. comm.). Both sexes often urinate
while scent-marking. In P. edwardsi, dominant individuals of both sexes mark more than subordinate
individuals. Female scent-marking rates are not highest during the mating season, but peak just
before during the lactation/dispersal season. Similarly, male rates also peak during the dispersal
season (Pochron et al. 2005a; 2005b). The chemical composition of P. edwardsi ano-genital gland
secretions differs between the birth and mating seasons, and could be due to seasonal differences
in diet or hormone levels (Hayes et al. 2006). Males scent-mark twice as often as females
(Pochron et al. 2005b). However, female scent-marks are responded to far more often and more
quickly than male marks. In P. candidus, for example, only 17% of male marks are responded to by
other group members but 71% of female marks received a response on average within 61 seconds
(Patel 2006b). In both P. edwardsi and P. candidus, male overmarking of a female's mark is the
most common response, followed by males overmarking the scent-marks of other males. Male eastern
sifakas preferentially use one type of scent-marking, combined chest-ano-genital marking, when
depositing an overmark (Andrianandrasana et al. 2007). The high rates of overmarking practiced
by male eastern sifakas lead to totem-tree marking in which certain trees are covered with male
gouge marks which probably reflects competition for females. Totem-trees may occur along territorial
borders, but are generally observed throughout the home range in P. candidus and P. edwardsi
(Powzyk 1997; Ritchie & Patel 2006; ER Patel pers. comm.).
Content last modified: February 4, 2008
Written by Kurt Gron. Reviewed by Erik Patel.
Cite this page as:
Gron KJ. 2008 February 4. Primate Factsheets: Diademed sifaka (Propithecus diadema) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/diademed_sifaka/behav>. Accessed 2015 March 2.